Weighing sensor for an electronic scale and electronic scale

ABSTRACT

The invention discloses a weighing sensor and an electronic scale provided with the same. The weighing sensor comprises a flat plate formed into helical shape, including successively a load-supporting portion, a strain portion and a bearing portion from the center to the outer of this plate, with the load-supporting portion situated between and surrounded by the bearing portion and the strain portion; wherein the load-supporting portion and the bearing portion are respectively used to bear the acting force and the reaction force in opposite directions, and a strain gauge is mounted on the strain portion. The electronic scale comprises at least three weighing sensors, wherein the bearing portion of the sensor is mounted on the scale body, the load-supporting portion directly contacts the supporting leg of the scale, which contacts the plane on which the scale is positioned. The present invention has small thickness, simple structure and low manufacturing cost.

STATEMENT OF RELATED APPLICATIONS

The present application is a continuation-in-part application of theInternational Patent Application No. PCT/CN06/001392, entitled “A Sensorand a Scale Provided with the Same,” filed Jun. 20, 2006, and claimspriority to Chinese Patent Application No. 200620054396.9, entitled “ASensor and an Electronic Scale Provided with the Same,” filed on Jan.24, 2006, both of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to a sensor, in particular aself-supporting weighing sensor used in an electronic human weightscale. The present invention also relates to an electronic scaleprovided with three or more such sensors.

BACKGROUND OF THE INVENTION

The elastomer of a weighing sensor mainly comprises three parts, thatis, a first stress surface for transferring acting force, a secondstress surface for transferring reaction force, and a strain rodconnected between the first stress surface and the second stresssurface. In a general weighing sensor, one or two stress surfaces haveto be riveted or screw-fixed onto a rigid base frame or a supportingbeam for transferring the acting force and the reaction force.

The elastomer of a self-supporting weighing sensor is shaped by punchinga piece of sheet metal into two stress surfaces and a strain rod,wherein one of the stress surfaces forms a bearing frame to make thesensor itself stably disposed on the base frame of the scale body fordirectly transferring acting force to cut down the cost of the sensorand the whole electronic scale without fixing a supporting beam onto thebase frame via a hard connection.

In order to eliminate or reduce partial load and repeatability error ofthe self-supporting weighing sensor, the other stress surface of thesensor, which transfers reaction force, transfers the reaction force ina manner of point contact.

For the present, there are three kinds of common self-supportingweighing sensors used for the electronic scales. The first kind is of“M” type structure, as shown in FIG. 12, of which the particularstructure is described in detail in U.S. Pat. No. 5,929,391, publishedon Jul. 27, 1999; the second kind is shown in FIG. 13, of which detailsare described in CN patent application No. 96106220.7, published on Jul.2, 2003; and the third kind is of “E” type structure, as shown in FIG.14, of which details are described in CN patent No. 200420015320.6,published on Apr. 6, 2005.

The first kind, i.e., the sensor with “M” type structure, has a bearingframe for self-supporting and a load-supporting point for transferringthe reaction force, and is convenient for installation. However, it hastwo strain rods, and the strain gauge must be bonded to each of them toensure precision, which highly increases the cost. The second and thethird types of sensors introduced in above patent documents both havebearing frames for planar self-supporting, but the other stress surfacecan not directly be stressed, so load-supporting portions arenecessarily added to achieve point stressing, which is also costly.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a sensor with lowmanufacturing cost, simple structure and small thickness. Another objectof the present invention is to provide a scale provided with three ormore such sensors. To achieve the above objects, the present inventionadopts the following technical solutions.

According to the first aspect of the invention, there is provided aweighing sensor, comprising a flat plate formed into a helical shape,which includes successively a load-supporting portion, a strain portionand a bearing portion from the center to the outer of the helical flatplate, with the load-supporting portion situated between and surroundedby the bearing portion and the strain portion; wherein theload-supporting portion and the bearing portion are respectively used tobear the acting force and the reaction force thereof which are oppositein directions; and a strain gauge is mounted on the strain portion.

Optionally, in the weighing sensor according to the first aspect of theinvention, a spherical or conical protrusion or depression is providedon the load-supporting portion so that the acting force directly acts onthe top end of the protrusion or the bottom end of the depression.

Preferably, in the weighing sensor according to the first aspect of theinvention, the bearing portion is in “C”-shape, surrounding theload-supporting portion from three sides, while the strain portion is inplanar-block shape, surrounding the load-supporting portion from theremaining side.

Further preferably, in the weighing sensor according to the first aspectof the invention, the strain portion and the bearing portion aresubstantially situated on same plane, while the load-supporting portionprotrudes from this plane via a step provided at the abutting sitebetween the load-supporting portion and the strain portion.

Yet preferably, the weighing sensor according to the first aspect of theinvention is integrally formed with one sheet metal.

According to the second aspect of the invention, there is provided anelectronic scale, comprising at least three weighing sensors accordingto the first aspect of the invention, wherein the bearing portion of thesensor is mounted on the scale body, the load-supporting portiondirectly contacts the supporting leg of the scale, and the supportingleg contacts the plane on which the scale is positioned.

Preferably, the load-supporting portion of the sensor makes pointcontact with the supporting leg, and there may exist relative movementbetween them. The supporting leg includes a base frame; a sensorsupporting plate is mounted in the base frame; and a cover plate ismounted on the base frame.

The beneficial effects of the present invention are as follows: theload-supporting portion, the strain portion and the bearing portion ofthe present invention are all formed out of the same piece of sheetmetal by punching, which may directly bear the reaction forcetransferred by the supporting leg of the scale, no need for additionallyfixing a metal support thereon. Therefore, the sensor with such astructure is simple in structure and for processing, low-cost formanufacturing, convenient for installing, and capable of making theentire electronic scale thinner and more fashionable.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further illustrated through embodiments inconjunction with the accompanying drawings hereunder, in which:

FIG. 1 is an illustration of a weighing sensor according to the presentinvention;

FIG. 2 is an illustration of a stress surface of a bearing portion ofthe weighing sensor according to the present invention;

FIG. 3 is a cross-sectional view of the weighing sensor according to thepresent invention along the direction A-A′;

FIG. 4 is a cross-sectional view of the weighing sensor according to thepresent invention along the direction B-B′;

FIGS. 5 and 6 show the position of the stressing point of aload-supporting portion of the weighing sensor according to the presentinvention on the stress surface of the bearing portion;

FIG. 7 is an illustration of an electronic scale provided with thesensor shown in FIG. 1;

FIG. 8 is a cross-sectional view of FIG. 7;

FIG. 9 is a partial enlargement view of the supporting leg shown in FIG.8;

FIG. 10 is a structurally exploded view of the supporting leg;

FIG. 11 is a partial enlargement view of the supporting leg;

FIG. 12 is the structure of one sensor in prior art;

FIG. 13 is the structure of another sensor in prior art;

FIG. 14 is the structure of further another sensor in prior art.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a weighing sensor according to an embodiment of thepresent invention as a whole is in a helical shape, and integrallyformed out of a piece of sheet metal. Along the helical line from thecenter to the outer of the helical flat plate are successively aload-supporting portion 4, a strain portion 2 and a bearing portion 3.The strain portion 2, shaped in flat block, has a strain gauge 1 mountedthereon, and can be bent and deformed under the influence of the weightto be measured. On both sides of the strain portion 2, theload-supporting portion 4 and the bearing portion 3 are providedrespectively for bearing the acting force and the reaction force whichare opposite in directions. The bearing portion 3 is in “C”-shape. Asseen from the whole of the helical sensor, the load-supporting portion 4is situated between the bearing portion 3 and the strain portion 2, ofwhich three sides are surrounded by the bearing portion 3, while theremaining side surrounded by the strain portion 2 shaped in flat block.As shown in FIG. 2, the shaded section is the stress surface of thebearing portion 3.

The load-supporting portion 4 may directly bear the acting force, noneed for an additional support fixed thereon. There is a spherical orconical protrusion or depression 7 on one side of the load-supportingportion 4, which bears the acting force. The force directly acts on thetop end of the protrusion or the bottom end of the depression, as shownin FIGS. 1 and 3. The load-supporting portion 4, the strain portion 2and the bearing portion 3 may be substantially situated on the sameplane. However, it is preferable to substantially situate the strainportion 2 and the bearing portion 3 on the same plane, while to make theload-supporting portion 4 protrude from this plane via the step 20provided at the abutting site between the load-supporting portion andthe strain portion, as shown in FIGS. 1 and 4.

FIGS. 5 and 6 show the position of the stressing point of theload-supporting portion of the weighing sensor according to the presentinvention on the stress surface of the bearing portion. The “C”-shapedbearing portion 3 fully surrounds the load-supporting portion 4 so thatthe protrusion or depression 7 on the load-supporting portion 4 issubstantially located in the middle of the stress surface of the bearingportion 3. There are at least three such points on the surface of thebearing portion 3 that bears the reaction force, so that the point(e.g., the protrusion or depression 7) for bearing the acting force orthe center point on the load-supporting portion 4 must be projected intothe triangle defined by said three points along the stressing direction,as shown in FIG. 6. Therefore, the sensor may be kept in balance whenthe load-supporting portion 4 and the bearing portion 3 bear the actingforce and the reaction force which are opposite in directions.

FIGS. 7 and 8 show an electronic scale having at least three weighingsensors according to the embodiment of the present invention. Thebearing portion 3 of the sensor is mounted on the base frame 8 of thescale body 5. The load-supporting portion 4 directly contacts onesurface of the supporting leg 6 of the scale, and the other surface ofthe supporting leg 6 makes contact with the plane on which the scale ispositioned. The load-supporting portion 4 of the sensor makes pointcontact with the supporting leg 6, and there may exist relative movementbetween them, as shown in FIG. 9.

As shown in FIGS. 10 and 11, the supporting leg of the electronic scaleaccording to the embodiment of the present invention includes a baseframe 8, a supporting leg 6 and a cover plate 9. The supporting leg 6 isconnected with the surrounding frame 11 through the elastic spokes 10;the surrounding frame 11 is fixed on the cover plate 9; and the coverplate 9 is fixed on the base frame 8. The bearing portion 3 of thesensor is mounted on the base frame 8 to bear the acting forcetransferred from the scale body. The spherical protrusion 7 on theload-supporting portion 4 of the sensor makes contact with the uppersurface of the supporting leg 6, while the lower surface of thesupporting leg 6 makes contact with the ground, and the reaction forceof the ground, via the supporting leg, is transferred to the sphericalprotrusion 7 on the load-supporting portion 4 of the sensor. Of course,the supporting leg may also adopt other structures, which are notdescribed in detail herein.

In addition, when there is a spherical or conical depression instead ofthe protrusion on the load-supporting portion 4 of the sensor, the uppersurface of the supporting leg 6 is correspondingly provided with aspherical or conical protrusion.

When the electronic scale is subject to a weight, the acting force andthe reaction force are respectively transferred to the load-supportingportion 4 and the bearing portion 3 to deform the strain portion 2,causing changes in the resistance of the strain gauge 1, and the valueof the weight is finally measured via an electronic circuit.

1. A weighing sensor, comprising a plate formed into a helical shape,which includes successively a load-supporting portion, a strain portion,and a bearing portion from the center to the outer of the helical plate,with the load-supporting portion situated between and surrounded by thebearing portion and the strain portion, wherein a strain gauge ismounted on the strain portion, and wherein the bearing portion issubstantially in a “C”-shape and surrounds the load-supporting portionfrom three sides, while the strain portion surrounds the load-supportingportion from the remaining side.
 2. The weighing sensor according toclaim 1, wherein the strain portion and the bearing portion aresubstantially situated on the same plane, while the load-supportingportion protrudes from this plane via a step provided at the abuttingsite between the load-supporting portion and the strain portion.
 3. Theweighing sensor according to claim 1, which is integrally formed withone piece of sheet metal.
 4. The weighing sensor according to claim 1,wherein the helical shape of the plate is in the form of a spiral. 5.The weighing sensor according to claim 4, wherein the bearing portionand the strain portion are in the same plane when no load is applied tothe bearing portion.
 6. The weighing sensor according to claim 4,wherein the bearing portion and the load-supporting portion are indifferent planes when no load is applied to the bearing portion.
 7. Aweighing sensor, comprising a plate formed into a helical shape, whichincludes successively a load-supporting portion, a strain portion, and abearing portion from the center to the outer of the helical plate, withthe load-supporting portion situated between and surrounded by thebearing portion and the strain portion, wherein a strain gauge ismounted on the strain portion, wherein the helical shape of the plate isin the form of a spiral, and wherein the bearing portion and theload-supporting portion are in different planes when no load is appliedto the bearing portion.
 8. A weighing sensor, comprising a plate formedinto a helical shape, which includes successively a load-supportingportion, a strain portion, and a bearing portion from the center to theouter of the helical plate, with the load-supporting portion situatedbetween and surrounded by the bearing portion and the strain portion,wherein a strain gauge is mounted on the strain portion, wherein thebearing portion is substantially in a “C”-shape is spaced from theload-supporting portion on three sides of the load-supporting portion,and wherein the strain portion is substantially rectangular and isspaced from the load-supporting portion from the remaining side of theload-supporting portion.
 9. The weighing sensor according to claim 8,wherein the substantially rectangular strain portion has curved ends.10. The weighing sensor according to claim 8, wherein the strain portionand the bearing portion are substantially situated on the same plane,while the load-supporting portion protrudes from this plane via a stepprovided at the abutting site between the load-supporting portion andthe strain portion.
 11. The weighing sensor according to claim 8, whichis integrally formed with one piece of sheet metal.
 12. The weighingsensor according to claim 8, wherein the helical shape of the plate isin the form of a spiral.
 13. The weighing sensor according to claim 12,wherein the bearing portion and the strain portion are in the same planewhen no load is applied to the bearing portion.
 14. The weighing sensoraccording to claim 12, wherein the bearing portion and theload-supporting portion are in different planes when no load is appliedto the bearing portion.